丝束同轴束源模式对电子束熔丝增材制造 TC11 钛合金组织及力学性能的影响

The presence of needle-like α′ martensite within the coarse columnar β grains is the primary reason for the poor ductility of TC11 titanium alloys produced by wire-fed electron beam additive manufacturing (EBAM). To enable the engineering fabrication of high-strength and high-ductile TC11 titanium alloys, a novel coaxial beam wire-EBAM (C-EBAM) process was developed, which could enhance the interaction between the electron beam, wire, and substrate, thereby improving the thermal distribution within the melt pool. Comparison between EBAM and C-EBAM samples was conducted, in terms of microstructures, grain morphologies, and mechanical properties. The impact of wire transition states on process stability, martensitic transformation, and the anisotropy of tensile properties was explored. The results reveal that C-EBAM facilitates the formation of strong lamellar α+β microstructure with minimal evaporation of Al elements, which is achieved through slow cooling within the β phase field and in situ martensite decomposition. Compared with EBAM, the enhanced ductility by C-EBAM is attributed to the development of the bi-lamellar microstructure and discontinuous α grain boundaries.